A quick way to measure the frequency of a waveform from the plot is to measure the time difference between adjacent peaks. You can do this by pointing to the peak and left-clicking the mouse button -- and while keeping the left-mouse button pressed, drag the mouse to the next peak. You should see a dotted line forming a rectangle. If you look to the lower left corner of the ltspice window, you will see the vertical and horizontal differences being reported. You can also use this technique to make vertical measurements as well. It is not as accurate as using the actual cursors (or using .measure statements), but it is quite easy once you get a hang of it. Try it out and see if it does the job!
Best regards,
v_c